This introduces a new per-user preference called
"Auto-play animated GIFs", which is enabled by default. When a
user disables this setting, gifs in toots become click-to-play.

Previews of animated gifs were changed to display the video play
button so that users can distinguish them from regular images.

This setting also affects account avatars in the detailed account
view, which was changed to use the same hover-to-play mechanism
that is used for animated avatars in timelines.

Fixes #1652

* jslint: remove trailing space

* jslint: fix no-nested-ternary issue

Follow the jslint [no-nested-ternary](http://eslint.org/docs/rules/no-nested-ternary)
rule. Rewritten ternary with if-then.

* When avatar/header are GIF, generate static versions.
Account API returns "avatar"/"avatar_static", "header"/"header_static"
Static version is the same as original for other cases
Web UI de-animates avatars in toots, lists of users

Fix #441, fix #596, prerequisite for #1064

* Fix JS test

* Add rake task to generate static avatars/headers from GIF ones, add test

adjusted to allow choosing it, yet

before. In the API, attachments now can be either image, video or gifv. Gifv
is to be treated like images in terms of behaviour, but are videos by file
type.

for those errors

The status is not showing anymore after clicking on it

Fix issue with detailed status view not supporting unreblogging/unfavouriting

nested inside a common parent (<Account>), instead they all embed <HeaderContainer />

application website validation, don't link to app website if website isn't set,
also comment out animated boost icon from #464 until it's consistent with non-animated version

Reflect "requested" relationship in API and UI
Reflect inability of private posts to be reblogged in the UI
Disable Webfinger for locked accounts

status clickable (this also fixes multiple dropdown being openable at the same
time)

on scrollable areas